The present invention relates to a motorcycle power train arrangement comprising a liquid cooled engine block and a transmission case, substantially exposed and mounted symmetrically to the longitudinal median plane of the motorcycle, largely filling the space between the front wheel and the rear wheel, and including a liquid coolant radiator mounted in substantially vertical position transversely to the direction of travel, a plurality of parallel cylinders being arranged transversely and a crankshaft longitudinally to the direction of travel, the transmission case being located under and/or behind the engine block, and a valve chamber cover forming a symmetrical outer longitudinal limit of the power train.
In a power train of this structure described in German patent application (Auslegeschrift) No. 2,538,172 the cylinders are arranged transversely in horizontally opposed pairs on both sides of the crankshaft which extends in the longitudinal median plane because, due to the wide lateral extension of the cylinders, the power train length is rearwardly limited by the space necessary for the driver's legs. In addition the double arrangement of cylinders, cylinder head, and intake and exhaust systems is disadvantageous in respect to structural complication and weight. It is also difficult to muffle the noise.
The object of the present invention is to provide a motorcycle power train in which these disadvantages are eliminated with a compact power train arrangement of efficient overall structure, including accessory elements, while retaining a low center of gravity. It is also intended to provide as much as possible for a flat and symmetrical configuration, low noise, and favorable conditions for the disposition of a compact exhaust gas treatment system near the exhaust line outlet from the cylinder head. The proposed object is achieved by providing that the cylinders are located on one side of the engine block in a single line; that the crankshaft is located on the other side of the engine block and is spaced from and parallel to the longitudinal median plane; and that covers for the valve chamber and a crank space form on both sides the symmetrical outer longitudinal limits of the power train. In the disclosed embodiment of the invention the covers themselves are substantially symmetrical. According to further features of the disclosed preferred embodiment of the present invention a portion of an exhaust system, on one side, and of a crankcase, on the other side, are adjacent to the covers, but less wide and substantially symmetrical. In addition, the liquid coolant radiator extends from the upper front edge of the engine block and substantially along the entire width of the power train.
Motorscooter and automobile power train arrangements of similar structure with horizontal cylinders are known from German patent Nos. 956,384 and 1,106,627 and German patent application (Offenlegungsschrift) No. 1,962,539. However the developments disclosed in German patent Nos. 956,384 and 1,106,627 provide for the short power train arrangement normal in motorscooters to permit free mounting between the front wheel and the covered air cooled power train, which is made possible by a transverse V belt drive or gearing located near the rear wheel. The structure disclosed in German patent application No. 1,962,539 is designed exclusively to propel automobiles and, in contrast to the invention, comprises a crankshaft extending perpendicularly to the direction of travel. All these structures are designed for installation in a casing, and are therefore of irregular shape and present gaps. Consequently the development of the invention and the application of these power train arrangements to motorcycles with exposed power train are not anticipated in these publications regardless of the existing demand. This is apparent also since these structures have been known for many years.
One embodiment of the invention is illustrated in the drawing.